Efficacy and Safety of PD-1/PD-L1 Inhibitors in Neoadjuvant Chemotherapy for Triple-Negative Breast Cancer: A Systematic Review and Meta-Analysis

Background: Compared with other subtypes, triple-negative breast cancer (TNBC) is more aggressive and has a lower survival rate with chemotherapy being the only acknowledged systemic treatment option. Recently, PD-1/PD-L1 (programmed cell death-1 and programmed death-ligand 1) inhibitors have demonstrated survival benefits in locally advanced or metastatic TNBC patients. However, the effects of PD-1/PD-L1 inhibitors in neoadjuvant chemotherapy remain controversial. Methods: Extensive literature searches were conducted in the PubMed, Embase and Cochrane databases. A pooled odds ratio (OR) with 95% confidence intervals (CI) was analyzed. Results: Seven randomized controlled trials (N = 1707) were included. PD-1/PD-L1 inhibitor chemotherapy group showed pathological complete response (pCR) benefit of 59.0% vs. 40.4% (OR 1.98, 95% CI 1.38-2.82, p < 0.001). Hematological adverse events were similar. There was no significant difference between the two groups in terms of anemia (OR 1.25, 95% CI 0.93-1.68, p = 0.14; I-2 = 0%, p = 0.99) or neutropenia (OR 1.00, 95% CI 0.82-1.21, p = 0.96; I-2 = 0%, p = 0.70). Conclusions: Adding PD-1/PD-L1 inhibitors to neoadjuvant chemotherapy can improve pCR rates in TNBC patients without increasing hematological toxicities. The data suggests that PD-1/PD-L1 inhibitors may be a viable option for patients with TNBC.